Combustion apparatus



April 16, 1929.

H. c. SIEBE RT COMBUSTION APPARATUS Filed May 20, 1924 2 Sheets-Sheet lINVENTOR 6i Swfieri ATTORNEY April 16, 1929. H. c. SIEBERT COMBUSTIONAPPARATUS Filed May 20, 1924 2 Sheets-Sheet iiitt t? INVENTOR a 49 wwfi,

ATTORNEY ,Patente'd I Apr. I 16,

- STATES 1,709,042 PATENT OFFICE.

s rnnr. comraur.

commission API'ARATUS.

Application filed May 20,1924. Serial No. 714,530.

My invention relates to combustion apparatus and it has for an object toprov de means in connection therewith for keeping the combustible gasesin the products of combustion at a minimum. V

More particularly, my invention has for an object to provide combustiblegas detectlng apparatus in connection with a furnace which detectingapparatus serves to regulate combustion. v

y A further object of my invention is to provide, in connection with ametallurgical furnace, or in connection with any furnace where thepresence of combustible gas is undesira- 1 ble owing to its chemicalreaction on materlal being treated, and which furnace or apparatus ismaintained at predetermined temperatures, means for detecting thepresence of combustible gas in the products of combustion, which meansoperates in conjunction with suitable pyrometric apparatus to providefor combustion to maintain a desired temperature with the presence ofcombustible gas in the products of combustion at a minimum.

An excess of air in the furnace means an excess of oxy en and thereforethe atmosphere is oxi izing. On the other hand, should there be anexcess of combustible gas, the atmosphere is reducing.

It is, therefore, an object of my invention to so control the relativeamounts of air and fuel admitted that, not only are desired andpredetermined temperatures maintained, but also the character of thefurnace atmosphere may be varied to suit different requirements. Inmelting furnaces, such as an open hearth furnace, the atmosphere may beoxidizing or reducing; and in heat treatment furnaces, such as heating,annealing, tempering, and tinning and galvanizing furnaces, theatmosphcre may be neutral or slightly reduc ing, but should not beoxidizing.

These and other objects are accomplished by my invention as will beapparent from'the following description taken in connection with theaccompanying drawings, forming a part of this application, in which: aFig. 1 is a diagrammatic viewof a furnace 50 showing my improvedregulating apparatus applied thereto; a

Fig. 2 is a diagrammatic view showing my improved regulating apparatusapplied to a furnace of the steam boiler type; and,

Fig. 3 is a diagrammatic view of a metallurgical furnace showing myimproved combustion regulating apparatus applied thereto.

Referring now .to the drawings for a better understanding of myinvention, in Fig. 1, I show a furnace, at 10, having a-fuel sup ly line11 and air supply line 12, the latter being provided with a suitablecontrol valve 13. The position of the valve 13 is regulated inaccordance with the amount of combustible gas in the 1products ofcombustion; and, to this end, I s ow a combustible gas detecter, at 14,which is sensitive to-combustible gas in the products of combustion andwhich operates, through a suitable relay, at 15, to control reversibleoperating means, at 16, for example, an electric motor mechanicallyconnected to the valve 13.

The combustible gas detecter is preferably of the Wheatstone bridgetype. The bridge comprises resistance arms 17 and 18 and arms 19 and 20connected in a parallel between the leads 21 and 22, which are connectedto any suitable source of current supply, the lead 22 preferablyincluding a rheostat 23 whereby the current passing through the arms ofthe bridge may be regulated. A conductor 24 is connected to the junctionat 25 between the arms 17 and 18 and a conductor 26 is connected betweenthe arms 19 and 20, the conductors 24 and 26 leading to a switch, at 28,of the galvanometer type which will be more particularly described.

The arms 19 and 20 include platinum wires extending through chambers 30and 31 and the current passing thercthrough' is regulated to maintain atemperature of substantially 800 F. in such wires. The chamber 31 isarranged to receive products of combustion by way of the conduit 32,which extends into the furnace, at 10. 1 A current of such products ofvcombustion through the chamber 31 is assured, as indicated by thearrows, by a suit-ableejector 33 which is connected at the end of thechamber 31-opposite to the connection of the conduit 32 therewith. Ifthe products of 100 combustion contain any combustible gases, such ascarbon monoxide or hydrogen, when they come into contact with the heatedplatinum wire in the chamber 31, catalytic action ensues, that is,combustion of the combustible 105 constituents takes place and thetemperature of the arm 20 is increased, with the result that theelectric resistance of such arm is also increased. Ordinarily therewould be sufficient oxygen in the products of combustion 110 to providefor combustion of any combustible gases as might pass through thechamber 31; however, in order to provide for any doficiency in thesupply of oxygen, I show an air supply conduit 34 connected totlieconduit 32, the inner end of the conduit 34 being connected to ascrubbing chamber 35 which, in turn, communicates with the atmospherethrough a port 36.

From the structure described, it will be apparent that a rise intemperature of the wire in the chamber 31 results in an increase inresistance thereof and consequently an unbalancing of the bridge withthe result that current flows through the conductors 24 and 26 to secureactuation of the coils of the galvanometer switch, at 28.

The galvanometer switch, at 28, includes any suitable movable coilelement in series with the conductors 24 and 26 or equivalent devicesand such element carries a contact member 37 which is arranged tocontact, with segments 38 and 39 separated by appropriate insulatingmaterial, at 40. The arm 37 is connectedto a conductor 42, which isconnected to any suitable source of electric current supply, as abattery 43. The segments 38 and 39 are connected by the conductors 44and 45, respectively, to the solenoids 46 and 47, respectively, and theother terminals of the solenoids are joined together and are connected,by the conductor 48, to the other terminal of the battery 43. Thesolenoids 46 and 47 are spaced apart a suitable distance and are insubstantial alignment. A switch arm 50 is pivotally mounted at 51 and ithas an arma- -ture element 52 disposed between opposing ends of thesolenoids 46 and 47. It will be apparent, therefore, that the armature52 and the arm 50 will be attracted either to the solenoid 46 or to thesolenoid 47 depending upon which of the contacts 38 and 39 is engaged bythe contact arm 37.

The arm 50 of the relay is connected to current supply lead 53 from anysuitable source and, at its upper end, it carries a con-- tact element54 for engagement with either of the contacts 55 and 56, connected,respectively, to the conductors 57 and 58 leading to the reversiblemotor, at 16. The other current supply lead 59 is connected directly tothe reversible motor. It will be apparent, therefore, that the relay, at15, is operative in opposite directions in respect to the combustiblegas content in the products of combustion in the furnace, at 10, tocontrol the direction of rotation of the motor, at 16, to move the valve13 either in an opening or in a closing direction.

In operation, assuming, that fuel in gaseous or liquid form is suppliedthrough the conduit 11 to the furnace and that the combustible gascontent of the products of combustion should increase, this would resultin unbalancing the detecter bridge, at 14, and the galvanometer switch,at 28, would be operated to move the arm 54 in a direction to so close acircuit for the motor, at 16, resulting in operation of the latter toopen the valve 13 wider so as to increase the air supply and reduce thecombustible gas. In operation, too much air may be supplied, in whichcase, the apparatus would operate to move the valve 13 in a closingdirection. To this end, the resistance arms 17 and 18 and 19 and 20 areso arranged that the bridge is unbalanced when the wire 20 is heated toa predetermined minimum extent above its normal temperature due to thepresence of combustible gases drawn from the furnace. \Vhen the bridgeis in equilibrium, the contact arm 37 will occupy a position over theinsulated separator 40 between the contacts 38 and 39 so that the valve13 is held in a fixed position so long as the quantity and qualit offuel supply shall remain constant. ombustible gas in an amount in excessof the predetermined minimum therefore, results in actuation of theapparatus to move the valve 13 in an opening direction to supply moreair for combustion. On the other hand, when the combustible gas tends todrop below the predetermined minimum, the bridge operates to securemovement of the galvanometer switch in the other direction and movementof the reversible motor 16 in the opposite direction to move the valve13 in a closing direction to cut down the supply of air.

The apparatus shown and described in connection with Fig. 1 isparticularly applicable to a furnace using gaseous or liquid fuels. Inso far as my invention is concerned, however, the principles are equallyapplicable to furnaces of other types, two of which will now bedescribed.

In Fig. 2, I show a furnace, at 61, of the ordinary steam generatingtype which includes a stoker 62 having an air supply conduit 63 providedwith a control valve 64, the latter being mechanically connected to arc- Versible motor, at 16. such as heretofore described. A combustiblegas detecter, at 14, is in communication with the combustion space orany place through which products of combustion pass; and, such detecteroperates in the manner already described to secure opening or closingmotion of the valve 64 in accordance with the combustible gas The valve70 is therefore regulated by a pyrgmetric device. A reducing atmosphereis maintained at a desired value by apparatus already described whichfunctions to control the degree of openness of the valve 68 in the airsupply. A desirable state of combustion is, therefore, maintained in thefurnace, at 66a substantially constant temperature is maintained bypyrometric regulation of the fuel valve 70; and, at the same time, forthe given predetermined temperature the reducing gas component of theproducts of combustion is maintained at a desired value by properregulation of the air supply in the Fanner already described inconnection with 1g. 1. Referring now to the pyrometric apparatus forcontrolling the fuel valve 70, I show a pyrometer 71' of a well-knowntype and which is suitably'located in the furnace, at 66. The leads 72and 73 of the thermo-couple of the pyrometer are connected to voltmetertype of apparatus 74 having an arm 7 5 adapted to engage with contacts76 and 77 connected, respectively, to the conductors 78 and 79 leadingto a reversible relay, at 80, which serves to move the valve 70 inopening and closing directions to regulate the quantity of fuel suppliedto the furnace for the purpose of maintaining a substantially constanttemperature. A drop in temperature indicates a deficiency in fuel andthe pyrometer responds to open the valve 70 wider to supply more fuel.An increase in temperature in the furnace has the contrary effect.

With the maintenance of a substantially constant temperature in themanner just referred to, the combustible gas detecting apparatusoperates to maintain the combustible atmosphere in the furnace at anydesired value by proper regulation of the air supply, thereby making itpossible to give proper heat treatment to any suitable material, such asmetal, at a predetermined temperature, without the danger of affectingthe chemical constituents of the material undergoing treatment in thefurnace to any deleterious extent. As shown in Fig. 3, the conduit 32for supplying a portion of the products of combustion to the detectingapparatus, at 14, has its lower end 81 arranged contiguously to thepyrometer so that each of these instruments shall be affected byproducts of combustion having substantially constant characteristics.

From the foregoing, it will be apparent, that I have devised combustionapparatus in which a closer regulation is maintained by properlycontrolling the air supply in accordance with the combustible gas in theproducts of combustion. It will also be seen that my improvedcombustible gas air regulating apparatus is particularly useful inconnection with a heat treatment furnace of any type wherein it isdesirable to maintain a substantially constant temperature While at thesame time avoiding the generation of an oxidizing or an excessivelyreducing atmosphere in quantities suflicient to affect chemicallymaterial being treated.

It is to be understood that, in so far as my invention is concerned, anysuitable character of fuel, solid, liquid or gaseous, may be used.

While 'I have shown my invention in a plurality of forms, it will beobvious to those skilled in the art that it is not so limited, but issusceptible of various other changes and modifications without departingfrom the spirit thereof, and I desire, therefore, that only suchlimitations shall be placed there upon as are imposed by the prior artor as are specifically set forth in the appended claim.

Having thus described the invention what I claim as new and desire tosecure by Letters Patent is:

In a metallurgical furnace, the combination of a conduit for supplyingair to the furnace, a conduit for supplying fuel to the furnace, valvesin the conduits, a'pyrometer in the furnace for controlling the positionof the fuel valve, and means responsive to the combustible gas contentof the products of combustion to control the air valve.

In testimony whereof I hereunto affix my signature this 12th day of May,1924.

HERMAN C. SIEBERT.

